How a C ++ object stores information about its member functions

class A {
       public :
       void printSometext() {
       std::cout << "printing A" << std::endl;
       }
    };
class B {
       public : 
       void printSometext() {
       std::cout << "printing B" << std::endl;
       }
    };

int main() {
   A* a = new A();
   a->printSometext();
   return 0;
}

As an object, C ++ stores information about its member functions. Let's look at the code above. When I call printSometext on the object "a", how does it know which function to call and how it finds the correct method. When printing the size of an object, it prints the summing size of its member variable (+ bindings). Therefore, please provide some internal information about how a member function is called.

Thanks Deimus